1. Field of the Invention
The invention relates to a dental prosthetic casting-on process and to a dental prosthetic primary part, which is suitable for the casting-on process.
2. Description of the Related Art
As an alternative to soldered, welded, cemented and precision-fitted connections, dental prosthetic components can be connected by casting-on. If a metallic connection with a closed joint is required for this, the joint component which is to be cast-on to (hereinafter designated the "primary part") and the joint component (hereinafter designated the "secondary part") which is to be cast-on, consist of an alloy which is made up of pure precious metals. As a rule high-carat, copper-free platinum- and iridium-containing gold alloys are used (cF. Lindigkeit in: G. K. Siebert: Dentallegierungen in der zahnarztlichen Prosthetik [Dental alloys in dental prosthetics], 1989, p880). If oxidizing alloys, e.g. a cobalt- or nickel-based alloy, are used, then provided the joint elements possess sufficiently retentive form, a tight connection is created initially. Due to the separating effect of the oxide layers on the joint elements, however, this latter exhibits an open metal joint apart from a few welded fusion points. This latter is soon attacked by crevice corrosion in the mouth and is enlarged. In the course of time the originally tightly-fitting elements can develop a distinctly visible and palpable loose fit which destroys the precision fit of the prosthesis.
Numerous dental objectives cannot be fulfilled by a single-casting process. As opposed to soldering or welding, the casting-on process avoids the additional problems associated with the transfer of sources of error involved in the production of a model for positioning and supporting the segments to be soldered; this results in a saving in both time and costs. The metallic cast-on connection using oxidising dental non-precious alloys is not considered possible in the-current state of the art.